Biotropica最新文献

Deforestation of tropical forests have resulted in extensive areas of secondary forests with the potential to restore biodiversity to former old-growth forest levels. The recovery of vertebrate communities is an essential component of biodiversity and ecosystem restoration, as vertebrates provide key ecosystem functions. However, little is known about the recovery trajectories and habitat preferences of vertebrates in tropical landscapes with differing land-use legacies. We used camera traps covering 3 weeks to study the activity of ground-based mammals and birds in the understory of 57 sites along a forest recovery gradient, ranging from active agriculture, such as pastures and cacao plantations, to naturally recovering forests and old-growth forests in the Chocó rainforest in north-western Ecuador. Our results show that diversity and biomass of wild vertebrates are highest in old-growth forests and late recovery stages, while for domestic vertebrates, these indices are highest in agricultural land. Additionally, while species-habitat networks showed low habitat specificity for vertebrate species, an indicator species analysis found no species to indicate old-growth forests, Dasyprocta punctata and Tayassu pecari to indicate all forest types, and Aramides wolfi and Pecari tajacu to indicate late regeneration forests. We suggest that these patterns are caused by a high habitat connectivity and large amounts of remaining old-growth forest in our study area. Our findings indicate that secondary forests have a high potential for the recovery of vertebrate species diversity and biomass to old-growth level in lowland tropical forests with short regeneration times.

Abstract in Spanish is available with online material.

Anthropogenic disturbances alter trajectories of ecological succession, introduce spatiotemporal variability in the composition of communities, and potentially create communities that differ substantially from those prior to disturbance. Invasive species are introduced or spread by human activities, with considerable effect on native ecosystems throughout the world. We evaluate the temporal stability of woody plant metacommunity structures and the mechanisms that give rise to them in a tropical disturbance-mediated environment. We used data collected over 20 years to (1) evaluate elements of metacommunity structure, (2) identify the gradients along which metacommunities are structured, and (3) quantify the relative contributions of environmental and spatial factors on variation in species composition. Analyses were conducted separately for combinations of life zone (areas defined by edaphic features and climate) and species origin (native versus non-native). Native species exhibited compartmentalized structures (i.e., groups of species with similar distributions that are replaced by other such groups along a gradient), whereas non-natives exhibited random structures. Metacommunities based on all species were consistently compartmentalized, except in dry forest, which exhibited random structure. Compartmentalized structures occurred along gradients defined by life zone and soil type, whereas no environmental factors were consistently associated with random structures. Metacommunity structure was stable through time despite a complex disturbance regime. Dry forests, which have experienced the most extensive and intensive history of anthropogenic disturbances of any life zone on Puerto Rico are characterized by degraded and fragmented landscapes, with species that do not respond to a common environmental gradient.

Agricultural induced land-use change comprises a key driver of biodiversity loss across tropical forests. Guinea-Bissau, among Afrotropical West Africa, was formerly occupied by native forest-savanna mosaics. While savannas have long given place to traditional rice agroecosystems, forests are now being transformed into cashew monocultures at unprecedented rates. The ecological impact of such rapid change is largely unknown. Here, we examined how rarefied species richness, encounters, and composition of amphibians and reptiles varied across forest remnants, cashew orchards, and rice paddies in northern Guinea-Bissau. To do so, visual encounter surveys were carried across 21 standardized sampling sites, seven in each habitat type. A total of 703 amphibian and 266 reptile encounters was recorded from nine and 14 taxa, respectively. The results show class-specific responses to habitat type. Amphibian richness was similar across habitat types, but rice paddies held more encounters and distinct composition compared to forest remnants. Reptile richness and encounters were lower in rice paddies than in forest remnants, but cashew orchards had the most encounters and a different composition compared to forest remnants. Overall, our results do not support the expected detrimental impacts of cashew expansion, which might be due to the still high heterogeneity of habitat types within the landscape. Rice paddies proved particularly important for amphibians, and for open-habitat reptiles, boosting the landscape-scale species diversity. In face of the eminent habitat conversion, maintaining heterogeneous landscapes, including the persistence of both forest remnants and rice paddies, is critical to minimize biodiversity loss in West Africa.

We report two instances of rescue behavior in wild Asian elephants (Elephas maximus) in Northeast India. Adult males assisted adult females sedated during GPS-collaring efforts, pushing them away from perceived threats. These behaviors meet the criteria for rescue behavior, providing evidence of prosocial and cognitively complex actions in elephants.

Abstract in Assamese is available with online material.

We found that increased rainfall reduced exuvial numbers and impacted populations of Taiwanosemia hoppoensis from coastal regions, likely due to prolonged soil flooding harming the subterranean nymphs. As climate change advances, long-term monitoring is essential to track cicada populations across taxa and regions, given their important ecological roles.

Abstract in Chinese is available with online material.

Elevational gradients represent platforms for exploring the effects of environmental variation on biodiversity. The environmental correlates of these spatial gradients are likely to be modified during the Anthropocene, as species respond to global change drivers including warming and increased frequency of extreme events. We quantified variation in the abundance of four functional groups of canopy arthropods (i.e., folivores, sap-suckers, detritivores, and predators), as well as in aspects of biodiversity on each of six host-plant species along two elevational transects in the Luquillo Mountains of Puerto Rico: a mixed forest transect, traversing tabonuco, palo colorado, and elfin forests, and a palm forest transect, comprising only patches dominated by sierra palm (Prestoea acuminata). We expected gradients in arthropod abundance and biodiversity to be host-tree specific, and for gradients on palm to differ between transects due to a combination of mechanisms associated with host selection, rescue effects, habitat structure, and source pool dynamics. In general, abundance and biodiversity declined with elevation. The ways in which abundance declined with increasing elevation was contingent on host tree identity and on arthropod functional group, whereas all aspects of biodiversity declined with elevation in consistent manners regardless of host tree identity or transect. Similarly, turnover (beta components of biodiversity between sequential elevational strata) did not differ between transects. Decreases in productivity with increasing elevation may be responsible for gradients in abundance or biodiversity. However, host-specific and functional group-specific gradients suggest that elevational effects manifest differently depending on tree species identity and resource bases that are consumer specific.

Savannas are complex ecosystems where multiple growth forms, including grasses, trees, and subshrubs, coexist through intricate ecological interactions. Understanding the mechanisms that promote this coexistence is key to conserving savanna biodiversity. This study investigated the effects of grass competition on the survival and growth of trees and subshrubs, as well as the interactions between these two growth forms. Using three species of trees and three species of subshrubs, we conducted a greenhouse experiment to assess how competition between trees and subshrubs is influenced by the presence of grass. We found that grass competition significantly reduced the survival of tree seedlings, while subshrubs were unaffected. When trees and subshrubs competed directly, subshrub biomass was reduced, but only in the absence of grass. Tree seedling biomass was not affected by subshrubs, but was negatively impacted by grass in the absence of subshrubs. Both root and stem biomass of trees and subshrubs were reduced by grass competition; however, this effect was mitigated when grasses, subshrubs, and trees competed simultaneously. These results indicate that when grasses, subshrubs, and trees compete together, the intensity of competition is reduced, promoting coexistence and contributing to the balance of growth forms in savanna ecosystems. While fire is an important factor in savanna dynamics, our study emphasizes the critical role of competition in maintaining this balance. Future studies should explore how fire and competition interact to further our understanding of biodiversity and ecosystem function in Neotropical savannas.

Abstract in Portuguese is available with online material.